Sparkplug Visual Diagnostics

[michael325e]

I changed my sparkplugs yesterday in my 84 325e. It had Bosch WR9LP that came with the car when I bought it and I put in NKG ZGR5A nickel. I have no idea how long the Bosch had been in it and it was running fine. And it seems to be running fine with the new ones, in the 10 miles or less I've put on it.

What I'm wondering is if there is anything the look of the old plugs can tell you about my eta engine.


GEDC0004 by Michael A2012, on Flickr
1-3

GEDC0010 by Michael A2012, on Flickr

4-6

GEDC0009 by Michael A2012, on Flickr

Thanks

[nando]

those are definitely the wrong plugs for an M20. I don't really like platinum plugs for any application, but on M20s they tend to make it run poorly.

they look pretty worn - the electrodes are totally fried (typical for a platinum plug that people think lasts 100,000 miles). maybe a tad lean on a cylinder or two, but the golden color is pretty good for the most part.

[michael325e]

Thanks nando. Are the NGK I put in ok? As a matter of education, what leads you to the lean diagnosis? Do you think I should clean my injectors? Also, when I was having my driveshaft replaced recently, a separate thread on this sorry subject, I noticed the O2 sensor wasn't connected. No idea why. We connected it. I haven't noticed any performance difference, though it is possible my gas mileage has gone down somewhat.

I did notice the erosion of the electrodes on most plugs, but as I say I have no idea how old they are.

Thanks,
Michael

[jlevie]

The plugs should be s bit darker, like a fawn brown. So I agree nado that the engine is slightly lean.